One of the most profound forms of chronic stress for the developing child is being subjected to abuse and neglect. As chronically stressed maltreated children develop, they are at substantial risk for substance use, abuse, and addiction. Thus, investigation of chronically stressed maltreated children provides a natural experiment for delineating the development of stress-induced vulnerabilities for substance use and abuse. Chronic stress exerts diverse negative effects on psychological and biological development, and understanding the impact of chronic stress on multiple developmental systems is critical for determining susceptibility to drug abuse. In this investigation, 400 chronically stressed maltreated 10-to 12-year-old children will be contrasted with 400 nonmaltreated children in order to determine the effects of chronic stress on neuroendocrine regulation, attention networks, executive function abilities, and emotion regulation capacities. Children will participate in a research day camp, and peer relations, personality organization, psychopathology, and substance use also will be assessed. Evaluations of child functioning in school will be obtained from classroom teachers, and the children's mothers also will provide information on additional sources of stress in the home. Based on a developmental psychopathology perspective and utilizing a person-centered approach, we expect to identify different forms of stress-induced vulnerability for substance use. The extent of aggregation of these forms of vulnerability within chronically stressed maltreated children who exhibit different types of personality organization and psychopathology will be investigated. The effects of additional forms of stress exposure and of a drug use promoting context on the susceptibility to substance use among children with different forms of vulnerability also will be investigated. The findings will hold promise for informing prevention and intervention initiatives.